Furnace with reflex arch



April 13, 1943. "P, WRIGHT 2,316,381

FURNACE WITH REFLEX ARCH Filed Oef. 16, 1939 3 Sheets-Sheet l April 13,1943. P, wRlGHT 2,315,381

y FURNACE WITH REFLEX ARCH Filed oct. 16, 1959 s sheets-sheet s PatentedApr. 13, 1943 geistig UNITED STATES ATENT OFFICE 2,316,331 FURNACE WITHREFLEX Anon raul Wright, Birmingham, Als. Application October 16, 1939,Serial No. .299,665

(ci. 11o- 72) v 11 Claims.

This invention relates to furnaces, and particularly such boiler andindustrial furnaces as utilize the various forms of wood fuels, refuseand other adaptable fuels.

The general object of my inventionis to provide, as a substitute for thecustomary dutch oven furnace, an improved furnace effecting a reflexmovement of the furnace gases over fuel therein moving progressively; afurnace attaining higher furnace temperatures with attendant hasteningof fuel burning; a furnace having an improved regulation andproportioning of combustion air through the fuel and over the fuel.

A further object is to provide such furnaces with protection of thelgrates and related parts against'heat; to facilitate the removal `of ashand cinder; to provide improvements infurnace enclosures to retain andutilize heat and reducel maintenance costs.

Another object is to provide a furnace that utilizes a reflex arch thatis exposed to furnace heat on both sides, whereby intense heat can bereflected below and above said arch within the furnace.

One feature of the invention is the provision for gravitationalplacement of fuel to transversely cover the grate uniformly and reposein greater thickness upon a lower adjoining hearth in comf bination.

Another feature of the invention is the provision for a steam generator,of a wood refuse burning furnace capable of sustaining high performanceratings, without employing supplementary fuels like oil or gas.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specic objects attained by its use,reference should be had to the accompanying drawings and descriptions inwhich I have illustrated and described preferred embodiments of thelnvention.

Of the drawings:

Fig. l is a longitudinal section illustrating one embodiment of myinvention.

Fig. 42 is a transverse vertical section taken at line 2--2 as shown onFig. 1.

Fig. 3 shows by enlarged view, the gas passages indicated at section 3-3in Fig. 1.

Fig. 4 is a longitudinal section illustrating a modification embodyingthe invention.

Fig. 5 is a. transverse vertical section on line 5--5 of Fig. 4.

Fig. 6 is an enlarged view of the uppermost grate rest.

Fig. 7 illustrates the application of the reflex arch and imperforatehearth, to the type of dutch oven furnace shown.

Fig. 8 furnishes an enlarged sectional View of the huid cooled tubes astaken at 8 8 in Fig. 7.

In the furnace embodying my invention illustrated by Figs. 1 and 2, afront wall I closes the portion forward of the grates, and an upwardcontinuation 2 and 3 provides a front wall portion, along which enteringfuel is fed into the furnace. Fuelv is delivered thru an opening 4,preferably across the entire furnace width; or there may be a series ofopenings ll locatedtransversely as shown. One form of roof enclosurecomprises a shape bounded by portions 5, 6 and 1 as illustrated in Figs.1 and 4. A wall 8 on each side extends upward from the foundations 9, onwhich the structure rests.

As the illustration of Figs. 1 and 2 shows the relation of the furnaceto a steam generator, I designate the lowermost water chamber I0, fromwhich water is conveyed thru pipes II, I2 and I3 to a tube header I 4 atthe upper front. A plurality of spaced tubes I5 extend from header I4,to a steam and water chamber I6. The assembly of pipes and tubes incombination with the steam generator forms a path of flow of water fromchamber I0 to chamber I 6. The spaced tubes I5 may be incased alongportions 5 and 6, with blocks and spacers similar to the constructionscovered by my patent application Serial 294,568 of 1935 series; orotherwise the space about tubes I5 is closed with refractory betweensame.

A front row of tubes I I support an upper front baffle I8 thru whichspaced openings I9 pass furnace gases between tubes v2i) and 2| beyond,whereby upper stratification of gases is relieved. Baffie I8 constitutesa downward continuation of the furnace roof 6, as defining the uppermostrear closure of the furnace of Fig. l. The primary heating surface lofthe steam generator is comprised of tubes I1, 20 and 2l.

The fuel support comprises a lowermost transverse grate support 22 uponwhich in close contact, is placed rest bar 23 as shown by Fig. 1.`

This construction supports the lower ends of grates 26, and resists thedownward thrust caused by the weight of grates and fuel thereon. Themasonry structure 3| beneath is an added safeguard to resist deflectionof the beam 22. Said masonry structure also functions as a furnacehearth in combination with said grates adjoining same. The hearth slopesas shown or it can be level.

An intermediate transverse grate support 22a with grate rest bar 24, isused to hold up the grate ends that abut. An uppermost transverse graterest 25 is also illustrated by an enlarged view Fig. 6. which shows howair passage is arranged and provision made for the upper grate ends toslide due to expansion or contraction.

The upper structural front 28 holds wall 2 and 3, supports header I4slidably and fastens to upper rest bar 25 as shown. Access to grates foradvantageously cleaning, while the furnace is in operation, is affordedby openings 29 whereby a steam lance can be used to blow thru the grateopenings or, in cases of excessive accumulation of ash or fused matter,a slice bar can readily be used. Upper grates 21 or upper parts ofgrates 2B generally have a minimum of clinker.

Natural draft air admission to the furnace setting beneath grates, maybe thru draft doorways 3S, that also serve for ash removal.

As an extension for supporting the fuel beyond the lowermost ends ofgrates 26,1 provide a hearth 3| made preferably of refractory havingarched passages 32 beneath as shown by Figs. 1 and 2. The number andlocation of ash doorways 3D is arranged to suit passages 32 for easy ashremoval. Forward of passages 32, I provide one or more draft gates 33that are raised or lowered by chain 3d which passes thru front wall I.Keeping the chains taut will hold the gates 33 from leaning. howevergate guides may be used. To effect a complete closure downward fromlower grate support 22, I employ a partit-ion 36 that extendstransversely and fastens at the lower side to guides 35. Thus with gates33 raised, air thru the front side may pass thru passages 32 or thrugrates above or thru both, depending on conditions of fuel bed effectingresistance to air flow. 'This partition 36 may be sloped to shed ashesfrom grates 2S to the floor forward of gates 33.

For introducing forced draft beneath grate-.s only, with gates 33 downor closed, I provide a passage 31, preferably thru the side wall 8 andforward of partition 33; however, if gates 33 be raised, this forceddraft may also pass thru passages 32. I have found that the height thatgates 33 are open, will somewhat tend to proportion the air how betweengrates and arched passages 32 but not with adequate control. I thereforehave embodied in my invention, another source of forced draft thruopening 38 which is rearward of the partition 3B. This arrangement ofair inlets thru passages 33, 31 and 38 provides several combinations ofair supply beneath the fuel thru grates and over the fuel from passages32 below, in an improved distribution.

In prior furnace constructions of the general character described andwith either flat or inclined fuel supports, the furnace gases ow awayfrom the fuel bed in the most direct route to the furnace chambers exit.Thus in the case of moderately wet bogged wood fuel, the moisture andvolatiles gasify and rise toward the furnace roof and pass outwardbefore air thru the fuel bed can reach or mix with same.

Hogged fuel is usually made from wood that is waste such as scraps,trimmings, edgings with bark; and these are chipped, macerated andreduced in size thru a machine called a hog whence the terni. Woodrefuse fuel often comprises varied mixtures of hogged fuel with sawdust, shavings, bark waste and the like, which pass by conveyor to afuel storage.

asiassi Heretofore endeavor has been made to retard the gas ow undersuch circumstances, with the intended purpose to accomplish most of thecombustion in the primary furnace. This retarding has not beenpractically accomplished especially at forced rates of firing.Furthermore, the late addition of needed air for combustion at a zonebeyond the primary chambers exit, does not promote as good combustion asis accomplished by earlier distributing air in the gas distillation zoneand under high temperature conditions. And still further, the admissionof air thru the roof of the 'furnace and at the fuel entrances has achilling effect, reducing the roofs useful radiation effect, and airthru the roof is not as desirable as supplying air lower down close tothe fuel bed. Various arrangements have been tried or introducing airthru the bridge wall on its forward side and such openings invariablyclog or close by slagging. affording only temporary inlets and thus itis difficult to avoid undesirable air variations.

Air passing thru the bridge wall at high velocity towards the fuel,tends to wait light fuel to settle beyond unburned, unless burned intransit. Also admitting air thru the rear of bridge wall results inlanning of gases and insufficient mixing, whereby combustion is notcompleted.

Noticeably dutch oven furnaces operating at high ratings with refusematerials as fuel, often employ supplementary combustion chambers inwhich other fuels such as oil, gas or powdered coal are relied on toproduce high temperature radiant exposures that will aid in consumingthe carry-over of unburned fuel, as previously described.

To facilitate improvements in fuel burning, as compared with the dutchoven operations just described, I have invented a furnace constructionembodying a reiiex arch as illustrated in part by Fig. 1, Fig. 4 andFig. '7. The furnace may also comprise in part, a transverse ash pit 39spaced beyond the refractory hearth structure 3| and closed on the rearby a transverse bridge wall 4c. Refractory lined doorways 4| in eitheror both side walls 8 afford access for raking out or for inspection.Adjoining the transverse wall t5 above and inclining over the pit 39 andhearth 3 l. there is extended a reflex fluid cooled arch 62 which spansthe furnace between side walls 8. This reex arch 132 inclines somewhatparallel to the grate surface but not necessarily.

In the case of wide furnaces it is optional to provide a furnacepartition wall 43 as shown in Figs. 1 and 7. This wall 43 is notillustrated in Fig. 4. The partition wall 3 is arranged across the pit39 and hearth 3| so as to extend upward to the arch 42 and is usuallylocated midway between the side walls 8. Wall d3 is advantageous toabsorb heat, which can be radiated when wet fuel enters the furnace orwhen the grates 26 are cleaned, with fire retained on hearth 3|. Sideaccess doorways 46 are placed in side walls 8 also just above the top ofhearth 3|, there are provided appropriate doorways 45 for slicingclinker off hearth 3| into pit 39 below.

For further facilitating ash or clinlcer removal in combination withraising gates 33, I provide a transverse trench 45 which is covered byremovable plates 41 whereby with plates 47 in place, the rakeout is oversame thru doors 30 or with plates 41 removed, ash is deposited in trench155, to be moved away, and thereafter plates 41 are replaced to cover46.

Referring particularly to Fig. 4, I have shown an approximate uppercontour of the fuel when Asingle source without the burning wet hoggedsouthern pine; also from my observations made in practice, I have shownthe travel of combustion flames and gases. In like manner in Fig. 1, bymeans of arrows I show the direction of flow of air and gases thru thefurnace and beyond. In Fig. 4, I illustrate the preferred placement offuel on the grates 26 and hearth 3|, whereby the thicknessof the fuelbed gradually increases to a maximum thickness over the hearth 3| andbeneath arch 42. The fuel uniformly can cover the grate transversely ofthe furnace, which facilitates a controllable passage of air thru thefuel without blowing holes thru the re bed.

It is practical to operate 'the illustrated embodiments of my inventionby providing natural draft alone thru doors 3U; natural draft thru doors30 along with forced draft thru passages 32 from inlet 38 with gates 33closed or down; forced draft from inlet 3' I and doors 30 closed, thrugates alone with gates 33 closed or thru grates and passages 32 withgates 33 lifted, as desired. Another useful method of air supply is tosupply forced draft thru openings 31 and 38 with gates 33 closed, andbeing supplied from a furnace or from separate individual sources as maybe desired. Damper controls on ducts to 31 and 38 from the same sourceof air supply will separately vary the flow thru gates and over fuelunder the reflex arch. Again, separate sources of air supply thruopenings 31 and 38 permit variations in air quantity and pressuresbeneath the fuel and over the fuel. Y

Heretofore grates in many wood burning furnaces have given trouble dueto overheating and clinkering; various forms of pusher bars have beentried to advance fuel and move clinker; also disposal of ash and clinkerrepairs and shut-downs. Further record of such operating diflicultieswith pusher grates, is the trial usage of these in combination withwatercooled tubes; however such means does' not eliminate the causes ofdepositing slag or cinder on said grates. My invention improves uponthese conditions as will be understood from my specification andillustrations of this invention, as pertains to these features.

In the present construction, instead of using dump grates or theequivalent, to dispose of clinker that may-collect at the lower sectionof the grates, I employ an inclined hearth in combination with a reflexarch above, whereby the heat is so intense as to melt and collect andrunoi the clinker as illustrated in Fig. 4 at top of hearth 3 I. Spilledfuel in the rear of pit 39 burns intensely with air thru passage 32 andbridge wall 40 reflects heat against a thick mass of charred fuel in theregion or elevation of door 44. Thus ash, sandy matter and the like,settle to the bottom of the fuel on hearth 3 I, lndicatedj clinkergathers on lower ends of grates at 1c. If A 26, it will generally meltand run downward to the hearth; yet while it is soft, it can be slicedfrom doors 29 if it adheres to the grates. Use of a steam lance atnecessary intervalswill remove from the grates such ash, sand andsubstances that make clinker, before they become sticky 0r viscous. Whenthe furnace is operating at lower than average temperatures, the doorsmay be used to slice hardened clinker off the hearth and a cleavagebetweenthe hearth and clinker is assisted by utilizing the coolingsection, employing tube 55 as shown.

` Heretofore in dutch ovens, an inclined step has caused costly gratearranged with a. dump grate at the lower part has been used. andendeavor has been made to control the thickness of fuel bed by a widthof throat at the fuel entrance whereby 4the fuel would burn out bythetime it progressed to the dump grate, thus intending to providev a thinre at the bottom enabling ash and clinker to be dumped; but experiencesshow such dump grates are not satisfactory because the fuel at timesavalanches over same and against an adjacent bridge wall and results inclinkering and burning of the lower grates.

This burning is due to intense heat vabove and air passages being partlystopped by slagging on l the dump. Again, step grates have been usedwithout a dump grate 4where the fuel regularly avalanches onto a shelf,to pile up against the adjacent bridge wall and at an elevation belowthe ends of said grates. Here also a. deficiency of air neededover thefire occurs, as air does not suitably pass thru this piled fuel whereash and cinder accumulate on the said shelf.

An improvement wanted in fuel burning, is accomplished with my newcombination of a fuel support having a lower hearth adjoining an ash pitopen to the furnace'and a reflex archdirecting the gases of combustion,allin the manner described and as shown by the drawings.

With further referencevto ,the specification of the reflex iiuid cooledarch ,'42, shown by Fig. l, it comprises various blocks supported bysingle tubes 55 and doubletubes 55 extending across the furnace andresting on s lde walls 8. The tube 'acts as a beam andma preferredmaterial would be seamless steel tubing of a size and strengthcalculated to resist the weight of fuel and the blocks forming the arch.

As a means of practically constructing my reflex arch in extendedwidths,another preferred form of support comprises two tubes 56 as illustratedin Figs.y 1 and 7.. The double tubes 56 are incas'ed with blocks andspacers as shown and furnish a stronger and vstiffer beam than the samesize single tubes 55 shown.

In the wall 40 of Fig. 7 where tubes 55 appear, a means of-Afacilitating the erecting of tubes is shown by Fig'. 8 which isapartial section at 8 8 where tubes 55 pass thru wall 8. A clearancespace 64 above each tube 55 in wall 8 is provided and this may be packedwith removable mineral'wool for example. Thereby the' tubes are free toslightly move with the inner arch or wall which expands more than theouter part of wall 8which is` exposed to atmosphere.

Thel use of tubes 55 as utilized in the wall bounding refractory hearth3 I, serves to strengthen the construction v by bridging the upper partsof arches over, passages 32.

From the foregoing descriptiverspecication of the reflex archconstruction, it willbe apparent that theinclination of the arch 42 canbe suited to the upper contour of. thfe'fuel bed) in a manner to directcombustionair from pit 39 so as to be in intimate contact with the fuelas shown by Fig. 4f The extent of coverage of the'reex arch over thefuel bed is not limited by structural features of Support.

In Fig. 7. I show how this dutch oven furnace was improved by providingthe hearth 3|, ash and slag pit 39in combination with' wall 40 and arch42b. Alsothepartition wall 43a is retained, .the forward lower side ofwhich was, aligned with a bridge wall that was removed.

Heated air and gases from the fuel bed and pit below, pass far enoughforward by means of thereflex arch, to aid in heating and gasifying theentering fuel on the upper fuel support.V

Heretofore furnaces have been adapted to retain a thin bed of fuel in aninclined position with a forwardly sloping wall spaced therefrom tofor-m a combustion chamber between, said wall extending upwardly to thelevel of the upper grate; but such constructions fail to provide myimprovements utilizing the thick lower fuel bed, spaced close to myreflex arch for intensifying burning. with air admitted over the fuelfrom low down passages.

The reflex arch favors burning a thick fuel bed at the lower part of thefuel support whereby refuse in larger sized pieces can be burned underits intense reflected heat, yet the lower grates are protectedby thethick fuel as well. Also the thick fuel bed enables carrying a bankedfire not practical with a thin fuel bed.

The reflex arch effectually lengthens the gas travel from the lower partof fuel to exit of the furnace, by reason of the longer reflex path ofpassage, as compared with that in the customary dutch oven employing anapproximately vertical bridge wall. The invention provides animprovement in the rate and completeness of burning.

The combination of hearth 3| and arch 42 intensifies burning to theextent that grates 26 can be provided with small perforations or withoutperforations if desired.

The reflex arch being safely and practically held in position by fluidcooled tubular supports, it can withstand re on both exposed sideswhereby the upper side can usefully serve to radiate and reflect to thefurnace chamber above and gases traversing it. Practice shows fuel doesnot remain unburned over this arch.

Concerning the dutch oven roof construction as illustrated by Fig. '7,it has been common to suspend refractory tiles to match a desiredfurnace roof contoiu'. While such roof tiles are replaceable, the heatradiation loss and the maintenance cost is greater, than that of myfluid cooled roof 5, 6 and 1 of Figs. 1 and 4.

By illustrating preferred shapes of furnace roof enclosures and 8 as inFigs. 1 and 4, I desire to show that an enclosure of this type can besuited to various furnace and reflex arch constructions as related toboilers, in a manner to withstand intense furnace temperatureseconomically and and accommodate reflex movement of the combustion gasesas described.

It is practical and desirable to feed fuel across the furnace width thruentrances 4 as shown by Fig. 1 and Fig. 4 and between the spaced tubesl5.

Before the dutch oven of Fig. 'l was remodeled by adding the hearth 3|,pit 39, wall 40 and arch 42h of this invention, it was customary toprovide a thin fuel bed at the bottom of grates 26a, also air enteredthru dump grates adjoining the lower ends of grates 26a. A fuel bedthick at its lower part similar to that of Fig. 4, would thereforehinder air passage thru the lower grates 26a if employed in the furnaceof Fig. 'I not equipped with the above named hearth, pit, wall and arch.Hence the disadvantage of slagging on dump grates is avoided byimproving the furnace like Fig. '7 shows. It usually requires more thanan hour daily toclean one set of dump grates of slag, and the time andexpense saved by my invention' makes it,u seful to facilitate continuousfurnace performance.

In the case of burning light comparatively dry wood shavings, it ispossible with excessive forced draft and a thick fuel bed, to waftunburned shavings beyond the reflex arch, therefore I provide a dropcombustion chamber B6 as shown in Figs. 1 and 4. The ratio of hearthlength to grate length can be advantageously increased when burningshavings; and in such case the hearth can be approximately level, sincedry shavings make less ash than hogged fuel" which may contain sand. Thefuel on the floor at 66 will burn-readily upon admitting air thrudoorway 6l, provided the chamber is hot enough to promote combustion. Ifthe chamber is only moderately hot, an improved means for rapidlyburning the fuel, only to clear the floor, is had by employing a steamjet thru openings 68 as shown in Fig. 1, and air is admitted thruopenings 68 thereby.

In the present construction shown by Figs. l and 4, I employ a bafe 69that is supported by tubes 20 and 2l, as a means to direct the furnacegases rearward over the reflex arch and thence over the steam generatorsprimary heating surface. A special feature that eliminates a gas pocketin the uppermost furnace chamber adjacent said steam generator at thetop of baffle 69, provides for gas passages I9 as shown by Figs. 1 and3. Similar passages in Fig. 4, are designated at These openings i9 andl9a, serve to shunt upward portions of the combustion gases, whichcauses floating unburned fuel to rise in a flurry that increases itstime in transit and improves burning of same. In Fig. 1, the perforatebaille I8 corresponds to a downward extension of the roof 6, to adjoinbale 69, with the openings I9 occurring just above the baille 69.

I have previously stated that my invention utilizes other adaptablefuels. For example, as an overfeed method of firing coal, the novelimperforate hearth functions to reduce slagging of the grates.Furthermore, coalsV that have low temperature fusion of ash properties.will burn in improved manner, since the ash can melt on the hearth andpass to the slag pit.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best forms of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

l. In combination with a furnace: side walls, a front wall and a furnaceroof, extending between the side walls, and a fuel entrance into saidfurnace; within the furnace, a transverse imperforate hearth spacedinwardly from said front wall, a transverse fuel support comprised ofinclined grates that upwardly adjoin said front wall and downwardlyadjoin said imperforate hearth; a lower ash pit inwardly of and adjacentsaid hearth, said hearth sloping to and terminated by said transverselower ash pit; a door in the side wall at said pit; a heat reflectingbridge wall adjacent to the hearth but spaced apart by said pittherebetween; a heat reflecting arch joined to said bridge wall andextending over, and spaced apart from, said pit and hearth; said archbeing imperforate and extending upwardly toward said roof but spacedapart therefrom, to provide a furnace passage therebetween; thecombination being capable of effect- 42. The construction ing thereduction of cumulating the slag on said hearth, from whence it can passto said pit.

of claim 1, in combination with a door in the side wall and said doorsituated to enable the operator to slice slag voff said hearth into saidpit.

3. In a furnace, fuel burning apparatus-coinprising, a furnace frontwall, furnace side walls and inclined perforate said front walltransversely between the side walls; a furnace imperforate roofextending between the side Walls and to said front wall, and a fuelentrance into said. furnace; a level imperforate hearth adjoining thelower transverse edge of said grates; an ash pit arranged at therearward transverse edge of said hearth and a door in the side wall tosaid pit; a bridge wall across the furnace and so arranged that saidbridge wall and hearth form opposite sides of said pit; a refleximperforate arch that adjoins said bridge wall and thence extendsrelatively close to said hearth and grates; said arch extending upwardlytoward said roof but spaced apart therefrom, to provide a furnacepassage therebetween; an air supply chamber that is partially bounded bythe furnace front wall, and said side walls, and by said grates abovethe chamber; said front wall having air entrance doors therein; meansforming passages under said hearth to connect said air chamber to saidpit; doors arranged in the front wall of said air chamber, whereby anoperator can clean said grates by ejecting residue on to said hearthwhence the residue can be passed to said pit.

. 4. In combination with a furnace for burning solid fuel: side walls, afront wall and a furnace roof extending between the side walls, and afuel entrance into said furnace; within the'furnace, an inclinedimperforate hearth, an ash pitlextending transversely of the hearth, atransverse fuel support comprised of an inclined grate surface thatupwardly extends to said front wall and downwardly adjoins saidimperforate hearth the pitch of said hearth of repose of the fuel to beburned, and less than that of the inclined grate; said hearth sloping'to and terminated by said ash pit; a heat reflecting bridge walladjacent to the apart by said pit therebetween; a heat reflecting archjoined to said bridge wall and said arch extended over, and spaced apartfrom, said pit and hearth; said arch being imperforate and arranged toprovide a fuel burning passage between said fuel support and said arch,whereby fuel in large pieces will repose on the fuel support withoutsubstantially spilling into said pit, facilitating the burning of saidfuel which is subjected to intense reected heat.

5. In combination with a furnace for burning solid fuel: side walls,-afront wall and a furnace roof, extending between the side walls, and afuel entrance into said furnace; within the furnace an inclinedimperforate hearth, an ash pit extending transversely of the hearth, atransverse fuel support comprised of inclined grates that upwardlyadjoin said front wall and downwardly adjoln said imperforate hearth thepitch of said hearth being less than the angle of repose of the fuel tobe burned, and less than that of the inclined grates; cleanout doorsarranged in the side walls, above said grates; said hearth extending toand terminated by said ash pit; a door in each side wall at said pit; aheat reflecting bridge wall slag on said grates by acgrates that extendfreni being less than the angle hearth but spaced adjacent to the hearthbut spaced apart by said 4 roof but spaced 5 pitvtherebetween; a heatreflecting arch joined to said bridge wall and extending over, andspaced apart from, said pit and hearth; said arch being imperforate andextending upwardly toward said apart therefrom, to provide a furnacepassage therebetween; a partition wail arranged under said arch andacross said pit and hearth; the combination enabling burning fuel to beheld on said hearth, with said grates bare of fuel,thereby permittingsaid grates to be cleaned while re is retained in said furnace and heatis maintained in said partition wall to aid combustion.

6. In a furnace, for burning solid fuel, a slagging hearth-inclinedgrates for supporting fuel and said grates adjoining and extendingupwardly from said hearth; an ash and slag pit arranged along thelowermost transverse edge of said hearth; an air chamber arrangedbeneath and partitioned apart from said grates, means forming passagesarranged to connect said air chamber to said pit, which passages extendunder a fuel entrance into'said furnace; an imperforate lower transverseedge of a front furnace and as one source of air supply, a grate airchamber arranged under said grates and partially bounded by, said frontwall and said side walls. and a gated partition that adjoins the lowertransverse edge of said grates at said hearth; access doors in saidfront wall whereby air enters forward of said partition into said gratechamber; and as another source of air supply, a pit air chamber arrangedbelow said hearth and connected with combination air and ash passagesextended under said hearth to said pit; a door in said side wall wherebyair enters said pit chamber, rearward of said partition; whereby thecombinations of air thus supplied, facilitate the hastening of fuelburning with higher temperatures in the furnace; and said passagesadvantageously permit removal of ash, thru said gated partition and saidfront wall access doors.

9. In a furnace utilizing hogged wood as fuel: a front furnace wall,furnace side walls and inclined perforate grates that extend from saidiront wall transversely between the side walls; a furnace imperforateroof extending between the side walls and to said front wall, and a fuelentrance into said furnace; a lower imperforate hearth adjoining thelower transverse edge of said grates; an ash pit arranged at therearward transverse edge of said hearth; a bridge wall across thefurnace and so arranged that said bridge wall and hearth form oppositesides of said pit; a reflex imperforate arch that adjoins said bridgewall and thence extends relatively close over said hearth and grates;said arch extending upwardly toward said roof but spaced aparttherefrom, to provide a furnace passage therebetween; said hearth havingan inclination less than the angle of repose of the fuel and less thanthat of the grates, so that fuel will repose on the hearth in greaterthickness than on said grates and without substantially spilling intosaid pit; an air chamber that is partially bounded by the furnace frontwall and side walls, also by said grates above the chamber; also saidchamber bounded further by a gated partition that zones air between saidgrates and passages that are arranged to connect said air chamber to.said pit, and said passages arranged under said hearth; a door in theside wall for air entering said passagesl as partitioned from said airchamber: whereby air passes to the furnace thus; with the gates of saidpartition open, air passes from said chamber thru said grates also thrusaid passages to said pit; furthermore with theV gates of said partitionclosed, air passes from said chamber thru said grates, and separatelyair entering thru said door in the side wall as partitioned off, passesvia said passages to said ash pit, thereby enabling improved regulationand proportioning of combustion air thru the fuel and over the fuel.

10. In a furnace burning hogged wood as fuel, fuel burning apparatuscomprising, a. furnace front wall furnace side walls and inclined stepgrates that extend from said front wall transversely between the sidewalls; a furnace imperforate roof extending between the side walls andto said front wall with a fuel entrance into said furnace; a lowerimperforate hearth adjoining the lower transverse edge of said grates;an ash pit arranged at the rearward transverse edge of said hearth and adoor in the side wall to said pit; a bridge wall across the furnace andso arranged that said bridge wall and hearth form oppositer sides ofsaid pit; a reflex imperforate arch that adjoins said bridge wall andthence extends relatively close over said hearth and grates; said archextending upwardly toward said roof but spaced apart therefrom, toprovide a furnace passage therebetween; an air supply chamber that ispartially bounded by the furnace front wall and side walls, also by saidgrates above the chamber; access doors in said Vfurnace walls wherebyair enters said chamber;

passages with gateways, arranged to connect said air chamber to said pitby extending said passages under said hearth; said hearth having aninclination less than the angle or repose of the fuel and less than thatof the grates, so4 that bogged fuel will pass over the grates to pile onthe hearth without substantially spilling into said pit also the fuelwill repose thicker over said hearth than over the upper area of saidgrates, thereby providing protection of said grates against furnace heatand air of combustion passed beneath said arch in the furnace.

11. A furnace with reflex arch, having in combination: side walls, afront wall and a furnace roof extending between the side walls and afuel entrance into said furnace: within the furnace, a transverseimperforate hearth spaced inwardly from saidv front wall, a transversefuel support comprised of inclined grates that upwardly adjoin saidfront wall and downwardly adjoin said hearth; a lower ash pit inwardlyof and adjacent said hearth, said hearth sloping to and terminated bysaid ash pit; a heat reflecting bridge wall adjacent to the hearth butspaced apart by said pit therebetween; a reflex arch joined to saidbridge wall and extending over, and spaced apart from, said pit andhearth; said arch being imperforatef and extending upwardly toward saidroof but spaced apart therefrom to provide a reflex` passage of thecombustion gases therebetween; and said furnaceV extended rearward oversaid reflex arch so as to provide a drop combustion chamber rearward ofsaid bridge wall, whereby unburned fuel carried over said arch will burnwithin the drop combustion chamber.

PAUL WRIGHT.

